District



Nrrnn STATES CHARLES R. MCBLAIR AND ALEXANDER A. RAFF, OF WASHINGTON, DISTRICT OF COLUMBIA.

PROCESS OF MAKING IRON PRINTS BY PHOTOGRAPHY.

SPECIFICATION forming part of Letters Patent No. 403,061, dated May '7, 1889.

I Application filed December 15,1888. Serial No. 293,697. (No specimens.)

To all whom, it may concern:

Be it known that we, CHARLES R. MOBLAIR and ALEXANDER A. RAFF, citizens of Maryland and New York, residing at Washington, in the District of Columbia, have invented certain new and useful Improvements in the Process of Making Iron Prints by Photography; and we do hereby declare the following to be a full, clear, and exact description of the invention, such aswill enable others skilled in the art to which it appertains to make and use the same.

Our invention consists in the use of a solution, hereinafter specified, and of a process adapted in connection with said solution for the reproduction of drawings and other works of art. Drawings, duo, have heretofore been reproduced in various manners, of which the following may be enumerated: First, in placing them within a frame in contact with sensitized paper and exposing the drawings and the sensitized paper to the action of solar light and then developing this copy. When 1t was desire to produce so-called blue prints, the developing means employed conslsted of certain acids, which it is unnecessary to herein specify; and to produce dark lines upon a lighter background the blue print was sub; ected to a discoloring-bath, and then treated with proper reagents. Another process of producing dark lines upon a lighter background consisted in developing the copy by the application of steam and aniline-oil. It has been found from practice and experience that blue prints are very objectionable when they are to be used for mechanical drawings for machine-shops and for architectural work, (he, on account of the great difficulty experienced in the reading thereof, making them exceedingly difficult to work from, and also because they fade upon exposure to light, and thus lasting for no length of time. It has also been found from practice and experience in the process above set forth for the production ofdark lines upon a lighter background that said hnes are not permanent; and the first of these processes requires a double operation, which results in adouble expenditure of time, labor and cost of material, resulting in so increasing the cost of the copies as to render them impracticable and placing them almost beyond the reach of those persons using such copies; and with the second of these processes a special apparatus is required for the development of the copies by steam, besides the loss of time resulting from the number of stages in the process, which also make such copies comparatively very expensive.

The object of our invention is to produce copies of drawings and other Works of art which shall have intensely black and permanent lines upon a white background, said copy thus presenting to the eye the same appearance as that of the original, and which copy requires the expenditure of no more time and labor than to produce the ordinary blue prints and can be made as cheap or cheaper than the said blue print.

To carry our invention into efiect the paper upon which the copy is to be produced is moistened with the following sensitizing solution, to Wit: water, one pint; sesquichloride of iron, two and one-half ounces; ammonia citrate of iron, one dram; nitric acid, one dram; tartaric acid, one dram; gelatine, three fourths of an ounce. The paper is then given a few minutes to dry, laid in an ordinary frame in contact with the positive to be copied, placed in the sunlight for about ten or fifteen minutes, then removed and developed by passing it through a bath of gallic acid, tannin, or any other of the well-known developing acids; but we prefer to use gallic acid, as we have found from practical experience that better results are obtained therefrom.

It will be clearly seen by the foregoing description that no skill in the art is required to produce prints by our improved process, and that any ordinary paper may be used. We do not limit ourselves to the precise proportions hereinabove specified, nor do we wish to be understood as limiting ourselves to the precise materials set forth, as We reserve to ourselves the liberty of varying such proportions and employing materials having equivalent chemical proportions.

Having fully described our invention, what we desire to claim and secure by Letters Patent is 1. The method of sensitizing paper for the production of prints and pictures in black lines by a solution of Water, sesquichloride of iron, ammonia citrate of iron, nitric acid, tartaric acid, and gelatine, in or about the proportions hereinbefore set forth.

2. The method of sensitizing paper for the production of prints and pictures in permanent black lines directly from a positive by a solution of Water, sesqnichloride of iron, ammonia citrate of iron, nitric acid, tartaric acid, and gelatine.

3. The process of reproducing drawings, which reproduction will present the same appearance as that of the original, consisting in first sensitizing the paper upon which the reprodm-I ion is to be taken, with the following CHARLES R. MCBLAIR. ALEXANDER A. RAFF.

Witnesses:

CHAS. I-I. BUTLER, J AS. N. FITZPATRIGK. 

